Exhaust muffling means



May 2, 1939.

G. c. STARKWEATHER ET AL EXHAUST MUFFIJING MEANS 3 Sheets-Sheet 1 Filed July 6, 1938 fNVE/VTUYS.

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y 2, 1939- G. c. STARKWEATHER ET AL 2,157,030

EXHAUST MUFFLING MEANS Filed July 6, 1938 3 Sheets-Sheet 2 A 770/?A/EY5- y 2, 1939- G. c. STARKWEATHER ET AL ,0

l EXHAUST MUFFLING MEANS Filed July 6, 1958 3 Sheets-Sheet 3 Patented May 2, 1939 UNITED STATES PATENT OFFIEE EXHAUST MUFFLING MEANS Application July 6, 1938, Serial No. 217,703

19 Claims.

This invention relates to improvements in mufflers or exhaust silencing means for internal combustion engines and the like.

One of the objects of this invention is to pro-- vide silencing means including a main passage and a by-pass or branch passage, and means for restricting the flow of gases through the main passage when the silencing means has a relatively low temperature, to render the same more effective when the engine is starting and when operating at low speeds. It is also an object of this invention to provide a muffler of this kind having a main passage and a branch passage, and in which the main passage is provided with a valve which may be actuated by means responsive to the temperature of the muffler for controlling the position of the valve. Another object is to provide a thermostatically controlled valve in the main passage which, when the muffler is cold, forces a greater part of the gases to flow through a branch passage and which is opened when the temperature of the muffler increases to permit gases to flow freely through both the main passage and the branch passage, to reduce the back pressure of the muffler. Another object is to provide a muflier with a valve in the main passage and thermo-responsive valve operating means which is exposed to the temperature of the gases flowing through the branch passage of the mufller. It is also an object of this invention to produce a muffier construction of this kind which is inexpensive and durable and which produces the maximum silencing effect when the engine is starting or operating at low speeds, and which will reduce the back pressure when the engine is operating at high speeds.

In the accompanying drawings:

Fig. "l is a longitudinal, central, sectional View of a muffler embodying this invention.

Fig. 2 is a fragmentary longitudinal, central, sectional view of an end of the mufiler, On a larger scale.

Fig. 3 is a fragmentary elevation, partly in section, of the muffler as seen from the other side, the outer shell of the mufiler being in section to show the interior of the muffler.

Fig. 4 is a fragmentary longitudinal view of the muflier showing the conduit or inner shell and the thermostatic means for operating the valve arranged therein.

Fig. 5 is a transverse sectional elevation thereof, on line 55, Fig. 2.

Fig. 6 is a fragmentary, longitudinal sectional view of one end of a muffier provided with valve actuating means of modified construction.

Fig. '7 is a sectional elevation thereof showing the inner shell of the muffler in elevation and the outer shell in section.

Fig. 8 is another longitudinal view of one end of the inner shell of the muffler, the outer shell being omitted.

Our improvements may be applied to the exhaust system of an engine in any suitable or desired manner so as to provide a main passage which is constructed with the principal object of providing a passage of low resistance to the flow of gases, and in which the silencing of the exhaust is of secondary importance, and a second or branch passage which is designed mainly with the object of effectively silencing the exhaust. and in which the resistance of the flow of gases is of secondary importance. The flow of the exhaust through these two passages is controlled by thermostatically operated means responsive to the temperature of the silencing means in such manner that at relatively low temperatures, the exhaust will be passed mainly through the high resistance passage to produce good silencing, and at higher temperatures, which result from a greater demand of power from the engine, the exhaust will be passed mainly through the low resistance passage to reduce the back pressure in the exhaust manifold of the engine. Preferably, though not necessarily, the two passages are built into a single muffler which has a main passage for the gases and a by-pass or side passage which parallels the main passage for at least a portion of the length of the muiiier. By way of illustration, we have shown our invention applied to a muffler of the straight-through type in which the exhaust gases may pass through a perforate conduit straight from the inlet of the muflier to the discharge thereof, but it will be obvious that this invention may also be applied to any other type of muffler.

The muffler shown has a housing including an outer shell A, one end of which is closed by means of an inlet head 13 having formed in one piece therewith an inlet duct 1), to which the exhaust pipe of an engine may be connected. The other end of the outer shell is closed by means of a discharge head C having a similar discharge duct 0, to which a tail pipe (not shown) may be connected. A housing of any other construction may be employed, if desired. The two ducts, in the construction shown, are also connected by means of an inner shell or conduit which forms the main passage of the mufiler. This shell or conduit may be made of one or more tubular parts, that shown including a tubular part Ill, one end of which is Welded or otherwise secured within the inlet duct 19 of the muffler, and is provided with a suitable opening which may be in the form of apertures, or of any suitable or desired form.

The inner conduit or shell shown also includes a tubular part It, which in the construction shown is formed integral with a radial flange or annular partition l5 having an axially extending flange 56 which may be secured to or engage the outer shell A. The transverse part l5, consequently, forms a baffle or transverse wall extending from the inner shell or conduit to the outer one. The part iii of the inner conduit telescopes into the part M and may be secured thereto in any suitable manner, such for example as by spot welding.

The inner shell or conduit shown also includes a tubular part l'i, one end of which connects with an end of the tubular part it and which is also provided with openings or a plurality of groups of perforations l8. These perforations may be similar to the perforations ii and may be of the well known type formed by means of longitudinal slits in the inner shell, the metal at one side of each slit being forced out of alinement with the metal at the other side of the slit so as to form a louve 18a extending over each opening, as shown in Fig. 5. Any other perforations or openings may, however, be used. The part l'i of the inner shell or conduit extends to the discharge duct 0 of the muffler. The transverse wall or bafiie i5 is provided with suitable holes or openings 19. Since the perforations ii are located in advance of the transverse bafiie l5 and the openings 18 are in rear of the bafile, it will be obvious that gases may pass through the muiiler through the main passage provided by the inner shell or conduit and through the perforations H into a chamber 2t and then through the openings l9 in the transverse baflie 15 into the chamber 21, whereupon these gases may again return to the main passage within the inner conduit through the openings or perforations is. The muffler is, consequently, provided with a side or branch passage which forms a by-pass around the main passage, and since the cambers 20 and 21 are of relatively large size to provide for expansion of the gases and also for silencing of sound waves, it will be obvious that if the greater portion of gases were passed around the by-pass through the chambers 28 and 21, greater silencing effect would be produced, but this greater silencing efiect would be accompanied by greater resistance to the flow of the gases, and consequently, by greater back pressure in the exhaust pipe.

When an engine is operating at slow speeds and while being started, the amount of back pressure built up by the exhaust is not great, for the reason that relatively small quantities of exhaust gases are passed through the mufiler. If, however, an engine is operating at a high capacity, for example, when driving at high speeds, greatly increased volumes of gas are forced through the muiiler, and consequently, in mulilers as heretofore constructed, higher back pressure results. We have, consequently, devised means in the muilier for causing the gases to be by-passed around the main passage when the engine is being started and operating at low speeds, and whereby the main passage will be wide open when the mufiier becomes hot so that the gases discharged through the mufiler will encounter the minimum of resistance and will,

consequently, build up a low back pressure and these means include a valve arranged within the main passage between the openings or apertures ii and 18 thereof. This valve is arranged, in the construction shown, in the tubular member l4 and is of the butterfly type, including a metal disk 24 suitably secured to a valve rod 25 pivoted in apertures in the tubular member M. This valve rod is arranged to be swung about its axis to move the valve from a restricting position shown in Figs. 1 and 2, to a wide open position in which the valve disk 2 lies in a plane approximately parallel with the axis of the inner shell or conduit, as shown in broken lines in Fig. 3. An end of the valve pin or rod 25 extending out of the inner shell part it is provided with suitable means for automatically swinging the valve into different positions, depending upon the temperature of the mufiier. Any suitable means may be employed for this purpose, and in the construction shown in Figs. 1 to 5, we have provided a bi-metallic thermostatic element 2i for this purpose, which is rigidly supported on a part of the mufiier at one end thereof, for example, by means of a bracket 28 secured to the part ll of the inner shell. The part of the valve stem 25 which extends out of the inner shell is provided with a suitable crank arm 29 having a crank pin 30 which extends into a bent over or hook portion 31 oi the end of the thermostatic element 21. Any other means for connecting the thermostatic element 2'! with the stem 25 of the valve for turning the same may be provided.

The thermostatic element is so constructed that when cold, it will occupy a position such, for example, as that shown in Figs. 1 and 2, in which the valve 2% will extend transversely of the inner shell or conduit in such a manner as to obstruct or restrict the flow of gases through the inner conduit. Preferably the valve does not fit tightly within the conduit so that when the valve is in its flow restricting position, some of the gases may flow through the main passage within the inner conduit, but the greater portion of the gases will be forced to by-pass the inner conduit. As the thermostatic element becomes heated, it will move the valve 24 toward its open position, in which it extends substantially parallel to the axis of the inner shell, as shown in broken lines in Figs. 3 and 4. In order to prevent the thermostatic element, after it becomes excessively hot, from moving the valve beyond the wide open position, a stop pin 32 may be provided which is secured to the part M of the inner shell and extends outwardly into position to engage the crank arm 25 and prevent further swinging of the same, as shown in Fig. 3.

t will be obvious from the foregoing construction that when the mufiler is cold, the valve will be in the flow restricting position in the main passage, so that when the engine is being started, the muffler will produce the maximum silencing efiect by forcing the greater part of the gases to by-pass the main passage through the silencing chambers 28 and 2 1. When the engine is running at moderate speeds such, for example, as in city driving, the thermostat will become only slightly heated and will continue to force the greater part of the gases to by-pass the main passage. When, however, the car is driven at higher speeds, the mufiier will become heated to a higher temperature so that the thermostatic element 2'! will move the valve into its wide open position, so that the back pressure of the mufiler is reduced to a minimum and so that the engine may develop its maximum power.

The balance of the mufiier may be of any suitable construction to provide additional silencing properties. By way of example, we have herein shown another transverse partition or baiile 35 extending from the inner to the outer shell and having apertures 36 through which sound waves may pass into a chamber 31 for silencing the noise of the exhaust. If desired, an intermediate shell 39 may be provided about perforate portions of the inner shell. This intermediate shell may, for example, be made in two or more parts having their adjacent longitudinal edges secured together so as to form between the inner and intermediate shells chambers 40 and 4| for silencing high frequency sound waves. It will be noted that these silencing means operate on the exhaust, regardless of whether the same passes through either or both of the passages of the muflier, but the action of these silencing means is more effective when the valve 24 is closed or nearly closed, since in that case, the flow of gas past these silencing means will be steadier or more uniform and the sound partly cancelled before it is exposed to the action of these means. Furthermore, it will be noted that the valve 24 when in closed or flow restricting position still permits some gas toflow past the valve and straight through the conduit or inner shell. The gas pulses and sound waves passing the valve at such times, when reunited with the part of the gas pulses and sound waves which have passed through the branch passage, will be out of phase therewith, thus resulting in a further cancellation of sound waves. By permitting some gas to pass the valve even when the same is in closed position, a. reduction of back pressure results. Any other silencing devices may be provided, if desired.

In Figs. 6 to 8 inclusive, we have illustrated a modified form of the thermostatic device for controlling the flow of gases through the main passage of the muffler, and this device has been shown as incorporated in the same type of muiller as illustrated in connection with Figs. 1 to 5. In this construction, the valve 45 has a stem 46 which is provided on its outer end with a crank arm 41 having a pin 48 which engages in a. slot formed in a hook member or bracket 50. The hook member or bracket is secured to one end of the tubular member provided with a plurality of corrugations 52 and secured at its other end to the inner shell part 53, for example, by means of spot welds as shown at 54. As this corrugated member becomes heated, it expands, and upon cooling, contracts to its initial length. Consequently, when the corrugated member is cold, the parts will occupy the positions shown in Fig. 6, in which the valve 45 is in the flow restricting position transversely of the main passage of the mufiler. As the corrugated tubular member becomes heated, it moves the valve toward open position, and in Figs. '7 and 8, the valve is shown in the full open position. Movement of the valve beyond its wide open position may be stopped in any suitable manner, for example, by forming a shoulder 55 on the hook member or bracket 50 which is so located that when the valve is in wide open position, as shown in Fig. '7, the shoulder 55 engages the valve stem 46 to prevent further movement of the member or bracket 50. In operation, the corrugated thermostatic sleeve shown in Figs. 6 to 8 is similar to the bi-metallic thermostat 21 disclosed in Figs. 1 to 5. In both constructions, the thermostatic element may, of

the muffler will be effective during ordinary driv-' ing and until the car is drive-n at high speeds. If desired, the thermostat may be selected so that a gradual opening of the valve will take place. Consequently, when operating at moderate speeds, the exhaust of the vehicle will be only partly silenced.

While the thermostatic device may be secured in any suitable or desired part of the mufiier, it will be noted that in the construction shown, the thermostatic devices are connected in heat conducting relation to the inner shell or conduit and are also located in a path of gases flowing through the by-pass about the main passage so that the thermostatic device will be subject to the temperatures within the muffler, regardless of whether the gases flow through the main passage or through the by-pass.

By means of this invention, it will be evident that a muffler constructed in accordance therewith will act to afiord the maximum silencing of the exhaust under conditions existing when very little back pressure develops, owing to the small volume of gas flowing through the mufiier. When, however, more power is demanded of the engine, the greater volume of gas discharged through the muflier rapidly heats the thermostatic element so that the valve is opened to permit gas to pass substantially without obstruction through the main passage, as well as through the parallel or side passage, so that the back pressure will be reduced to a minimum. The fact that there is less silencing at higher speeds than at low speeds or idling is not objectionable, since the noise of the exhaust is less noticeable at higher speeds because of other noises which occur at high speeds. By the use of the invention herein described, it is also possible to construct mufflers capable of producing very superior silencing effects at low or moderate speeds, at which the resistance to the limited flow of gases is of no importance, without having these superior silencing effects handicap the engine when operating at higher speeds.

We claim as our invention:

1. Means for muffiing the exhaust of an internal combustion engine, including means forming a main gas passage of relatively low resistance to the flow of exhaust gases, valve means arranged in said duct, means forming a second gas passage of higher resistance to the flow of said gases than said main passage and having greater silencing eiiect upon the exhaust and connecting with said main passage in advance of said valve, and means responsive to the temperature of gases passing through said mufiiing means for urging said valve into a position to obstruct the passage of gases through said. main passage when said muflling means are relatively cool and into an open position when said mufiiing means are hot.

' 2. Means for mufliing the exhaust of an internal combustion engine, including means forming a main gas passage, means forming a branch passage of higher resistance to flow and greater silencing effect upon the exhaust than said main passage, said branch passage being connected at its inlet and discharge ends with said main passage, valve means arranged in said main passage intermediate of the portions connecting with said branch passage, and means responsive to the temperature of said muilling means and connected with said valve means for moving said valve means into flow obstructing position when said muflling means is relatively cool to force gases to pass through said branch passage and to open said valve means when said muffling means becomes hot.

3. A muffler having shells arranged therein to provide a main passage for gases and a branch passage, a valve in said main passage, said valve occupying a position, when said muffler is cold to restrict the flow of gases through said main passage and cause gases to flow through said branch passage, and means responsive to changes of temperature of said mufiler for moving said valve toward open position when the temperature of said mufiier rises, to open said main passage.

l. A mufller having shells arranged therein to provide a main passage for gases and a branch passage terminating in said main passage, a valve in said main passage intermediate of the portions thereof in which said branch passage terminates and which when in closed position, restricts the flow of gases in said main passage, thereby increasing the flow of gases through said branch passage, and means responsive to changes in temperature of said mufiler to open said valve when the mufiler is hot to facilitate the flow of gases through said main passage.

5. A mufiler having a shell providing a main passage for gases and having an opening through which gases may pass, a second shell arranged to receive gases discharged through said opening in said first shell and forming a branch passage for gases, and a valve in said first shell arranged in rear of said opening and which may be moved into a position to restrict the flow of gases through said first shell and into an open position to permit gases to flow freely through said first shell, and means responsive to changes in temperature within the muiiler for moving said valve into open position when the temperature in the muifler is high and into flow restricting position when the temperature in the mufiler is low.

6. A muiller having a pair of nested shells spaced apart toform a passage for gases between said shells, and a passage within the inner shell, the inner of said shells having an opening through which gases may pass from one passage to another, a valve in said inner shell which, when in open position, permits substantially unobstructed flow of gases through said inner shell and which may be moved into position to restrict the flow of gases through said shell, and temperature responsive means in said muffier for moving said valve into restricting position when said muilier is relatively cool and into a less restricting position when said muffler becomes warmer,

7. A muffler having a perforate inner shell forming a main passage for gases, a shell arranged about and spaced from said inner shell and forming therewith a branch passage for gases, a valve in said inner shell with perforations located in front of and in rear of said valve through which gases may pass from said inner shell into said branch passage and from said branch passage back to said inner shell, and thermostatic means arranged within said mufiler for moving said valve into position to restrict the flow of gases to said main passage when the mufiler is cold and for moving said valve into open position when the mufi'ier becomes heated.

8. A muiiler including an inner shell providing a main passage for gases, a shell arranged about and spaced from said inner shell and forming therewith a b-y-pass for gases, a valve in said inner shell for controlling the flow of gases through said inner shell and through said bypass, said inner shell having openings arranged in advance and in rear of said valve through which gases may fiow into and out of said by-pass, a stem for said valve which extends out of said inner shell, and a thermostatic device arranged in said by-pass and secured to said inner shell and cooperating with said valve stem for moving said valve into open position when the muffler is hot and into flow resisting position when the muilier is cold.

9. A mufller including an inner shell providing a main passage for gases, a shell arranged about and spaced from said inner shell and forming therewith a by-pass for gases, a valve in said inner shell for controlling the flow of gases through said inner shell and through said bypass, said inner shell having openings arranged in advance and in rear of said valve through which gases may flow into and out of said bypass, a stem for said valve which extends out of said inner shell, a bi-metallic thermostat arranged in said by-pass and having one end thereof secured to said inner shell and having the other end thereof connected with said valve stem for moving said valve into open position when the mufiier is hot and into flow resisting position when the muffler is cold.

10. A muffler including an inner shell providing a main passage for gases, a shell arranged about and spaced from said inner shell and forming therewith a by-pass for gases, a valve in said inner shell for controlling the flow of gases through said inner shell and through said bypass, said inner shell having openings arranged in advance and in rear of said valve through which gases may flow into and out of said bypass, a tubular member provided with substantially annular corrugations and having one end thereof secured to said inner shell and the other end thereof connected with said valve for moving said valve into open position when the mufiler is hot and into flow restricting position when the muffler is cold.

11. A mufiler including an inner shell providing a main passage for gases, a shell arranged about and spaced from said inner shell and forming therewith a by-pass for gases, a valve in said inner shell for controlling the flow of gases through said inner shell and through said bypass, said inner shell having openings arranged in advance and in rear of said valve through which gases may flow into and out of said bypass, a stem for said valve which extends out of said inner shell, a tubular member arranged in said by-pass and having substantially annular corrugations and having one end thereof secured to said inner shell and the other end thereof secured to said valve stem for moving said valve stem into flow restricting position when the muffler is cold and into open position when the muffler is hot.

12. A muffier including an inner shell form ing a main passage for gases, a shell arranged about and spaced from said inner shell, and forming therewith a by-pass for gases about said main passage, said main passage having openings communicating with said, by-pass, a valve in said inner shell arranged with openings spaced in front of and in rear of said valve, a stem rotatable about its axis to move said valve into difierent relations to said inner shell and having a crank portion, a thermostat arranged in said mufller and engaging said crank portion of said valve for moving said valve into open position when the mufiler is hot and into flow restricting position when the mufiler is cool.

13. A mufiler having an inner shell forming a passage for gases and provided with perforations arranged lengthwise thereof, sound deadening chambers arranged in said muflier about said passage and communicating with each other and with said perforations to provide about said passage a by-pass including said sound deadening chambers, and a valve in said inner shell and movable into a position to vary the flow of gas through said passage and said by-pass.

14. A muffler having an inner shell forming a passage for gases and provided with perforations arranged lenghwise thereof, sound deadening chambers arranged in said mufller about said passage and communicating with each other and with said perforations to provide about said passage a by-pass including said sound deadening chambers, a valve in said inner shell and movable into a position to vary the flow of gas through said passage and said by-pass, and thermostatic means for controlling the position of said valve to open the same when the mufiler is hot and to move the same into flow restricting position when the mufiler is cool.

15. A muflier including an inner shell forming a main passage for gases, a shell arranged about and spaced from said inner shell and forming therewith a branch passage for gases about a portion of said inner shell, heat responsive means arranged in said branch passage, and flow controlling means in said inner shell which are actuated by said heat responsive means to restrict the flow of gases in said main passage when the mufiler is relatively cool and to permit free flow of gases through said main passage when said mufller is hot.

16. A mufiler including an inner shell forming a main passage for gases, a shell arranged about and spaced from said inner shell and forming therewith a branch passage for gases about a portion of said inner shell, heat responsive means arranged in said branch passage and secured on said inner shell, and flow controlling means in said inner shell which are actuated by said heat responsive means to restrict the flow of gases in said main passage when the muffler is relatively cool and to permit free flow of gases through said main passage when said mufiler is hot.

17. Means for mufiling the exhaust of an internal combustion engine, including means forming a main gas passage of relatively low resistance to the flow of exhaust gases, valve means arranged in said duct, means forming a second gas passage of higher resistance to the flow of said gases than said main passage and having greater silencing effect upon the exhaust and connecting with said main passage in advance of said valve, means responsive to the temperature of gases passing through said mufiling means for urging said valve into a position to obstruct the passage of gases through said main passage when said muflling means are relatively cool and into an open position when said mufliing means are hot, and sound silencing means common to both of said passages.

18. Means for mufiling the exhaust of an internal combustion engine, including means forming a main gas passage, means forming a branch passage of higher resistance to flow and greater silencing effect upon the exhaust than said main passage, said branch passage being connected at its inlet and discharge ends with said main passage, valve means arranged in said main passage intermediate of the portions connecting with said branch passage, means responsive to the temperature of said muflling means and connected with said valve means for moving said valve means into flow obstructing position when said mufiiing means is relatively cool to force gases to pass through said branch passage and to open said valve means when said mufiling means becomes hot, and sound silencing means operatively associated with said main passage and located rearwardly of said branch passage and which acts on all gases passing through either of said passages.

19. Means for muffling the exhaust of an internal combustion engine, including means forming a main gas passage, means forming a branch passage of higher resistance to flow and greater silencing effect upon the exhaust than said main passage, said branch passage being connected at its inlet and discharge ends with said main passage, valve means arranged in said main passage intermediate of the portions connecting with said branch passage, means responsive to the temperature of said muflling means and connected with said valve means for moving said valve means into flow obstructing position when said muflling means is relatively cool to force gases to pass through said branch passage and to open said valve means when said mufiling means becomes hot, said valve when in position to produce the maximum obstruction to the flow of gases, providing a passage for a small part of the exhaust through the main passage for mixture with the part of the exhaust which has passed through said branch passage.

GAIL C. STARKWEATHER. LUCIEN L. I-IAAS. 

